When you understand the definition of leadership, you will understand why leadership is everything.
In this article, we will define leadership in several ways and highlight how it plays out in practice. Let's begin with the simplest definition of leadership.

So, what is leadership?
Leadership is the ability to command acceptance by a group of people and thus, get them to do what the leader wants. The person providing this direction and commanding acceptance is called the leader.

From this definition of leadership, it is obvious that the leader is the person whom others accept to show them the way.
However, you probably are aware that a leader can be imposed on a group of people against their will. For example, a military coup can bring a leader to power. This leader was not voted for or accepted by his people. But he ascended the leadership seat by virtue of military might or military intrigues.

You may ask, can this military dictatorship be referred to as a form of leadership over the people?
Of course, yes.
Obviously, this indicates that our definition of leadership above is not all-inclusive. Something is missing. So, let's define leadership again.

What is leadership?
Leadership is the ability to provide direction to a group of people and influence those people to follow the direction and act accordingly.
This seems like a better definition. But it still does not take into cognizance the fact that a leader may not necessarily influence his people in the accepted sense of the word.

The word 'influence' suggests that the leader motivated people to follow his direction. Influence can also be defined as the ability of an individual or group of individuals to get others to conform to their expectations or requirements. Either way, it implies willing acceptance to follow the instructions or directions of the leader for whatever reason the individuals decide to do so.

But when the leader has to compel, force, or coerce people to do what he says, it is no longer influence. Nevertheless, the person who uses coercion, brute force or some other unethical means to get others to do as he says is still a leader.

That brings us to the realm of Leadership Styles.
A leader can be...
A charismatic leader
An autocratic leader:
A dictator:
... or whatever other leadership style he wishes to adopt.

Whatever his approach to leadership, he is still a leader.
Now that we have established that, let's refine our definition. Let's define leadership again in a manner that is all-encompassing.

I ask the question again: what is leadership?
Here's the simple answer.
Leadership is the ability to influence other people to act in line with your expectations willingly or otherwise.

Everything or anything the leader does to accomplish the goal of gaining followership merely defines the style of leadership. It does not define the concept of leadership.
Understand the true meaning of leadership. Understand how this affects you. Understand why people often say everything rises and falls on leadership. Then plug yourself in to reap the benefits of effective leadership.
Leadership is about results. It's about managing followers in such a way that you deliver on set objectives.

A leader may not achieve set objectives. A leader may be terribly disappointing and shallow but is he still the leader?

Well, if he is the man in charge, he is the leader.
So, there is good leadership and bad leadership dependent on the Leadership Skills of the leader. Leadership Development calls for a planned and repetitive practice to build or develop leadership skills and traits so as to enhance the quality of the results achieved.